Congestive heart failure (CHF), which is also sometimes referred to simply as “heart failure,” is a condition in which a subject's heart can't pump the needed amount of blood to the subject's other organs. Heart failure may result from a variety of causes, some of which include: a narrowing of arteries that supply blood to the heart muscle (coronary artery disease); a past heart attack or myocardial infarction, with scar tissue that interferes with the heart muscle's normal work; a high blood pressure condition; a heart valve disease due to past rheumatic fever or other causes; a primary disease of the heart muscle itself (cardiomyopathy); a heart defect present at birth (congenital heart defects); or an infection of the heart valves or heart muscle itself (endocarditis or myocarditis).
Heart failure can be conceptualized as an enlarged weakened heart muscle, which results in poor cardiac output of blood. As blood flow out of the heart slows, blood returning to the heart through the veins backs up, causing congestion in bodily tissues. This congestion may cause swelling in the legs, ankles, or other parts of the body and may also result in fluid collecting in the subject's thorax, which may become a barrier to normal oxygen exchange.
The fluid build-up in the thorax may result in pulmonary edema or pleural effusion. These conditions, if left untreated, may in turn lead to death. Pulmonary edema includes the build-up of extravascular fluid in the lungs. During pulmonary edema, fluid accumulates in extracellular spaces, such as the spaces between lung tissue cells. Pleural effusion, on the other hand, is the build-up of extravascular fluid in the space between the lungs and the rib cage. The lungs are covered by a membrane called the pleura, which has two layers, an inner layer and an outer layer. The outer layer lines the rib cage and diaphragm. The inner layer covers the lungs. The pleura produces a fluid, which acts as a lubricant to help in breathing, allowing the lungs to move in and out smoothly. Pleural effusion is the accumulation of too much of such fluid. Both pulmonary edema and pleural effusion, if they exist, present medical emergencies that require immediate (oftentimes challenging) care and can sometimes prove fatal.